Process and product for stabilizing of unsaturated hydrocarbons



Patented Sept. 1, 1936 PATENT OFFICE PROCESS AND PRODUCT FOR STABILIZING OF UNSATURATED HYDROCARBONS Charles P. Wilson, Jr., Houston, Tex.

N Drawing. Original application December 1'7,

19 30, Serial No. 503,095. Divided and this apphcatlon June 15, 1934, Serial No. 730,729

4 Claims.

This invention relates to a method of preventing deterioration of oils, fats, and rubber, and is applicable to substances liable to oxidation. The process and product will be de- 5 scribed more particularly in relation to inhibiting auto-oxidation of motor fuels resulting from pyrolysis of heavy oils or coal.

1 Color deterioration and gum formation are known to be the result of oxidation. Color de- 1 terioration does not render motor fuel or motor oil unfit for use, but lowers its market value. Gum formation is the result of oxidation of unsaturated hydrocarbons, and when present in motor fuel in'small quantities renders the fuel 15 unfit for use in an internal combustion engine. To obtain gum-free and stable products, the usual practice is to remove a substantial quantity of the unsaturated hydrocarbons through treatment with sulphuric acid, or through the control of the cracking plant in such a manner as not to produce a high concentration of the unstable unsaturated hydrocarbons. Control of the cracking process in this way sometimes results in a lower percentage of cracked fuel, and the sulphuric acid treatment always results in a loss, which in many cases runs as high as 5% of the motor fuel produced. This treatment is costly and wasteful, and also results in a lowering of the anti-knock value of the motor fuel.

The primary object of the invention is the manufacture and use of an oxidation inhibitor which, when added in minute quantities, prevents deterioration of hydrocarbons and various oils liable to oxidation. It is particularly useful in the manufacture and marketing of motor fuel containing unsaturated hydrocarbons liable to oxidation, since it not only inhibits gum formation in storage, but actually reduces the gum yield when the cracked product to which the inhibitor has been added is tested for gum by the copper dish method. In the majority of cases only a minute quantity of.'the inhibitor, the cost of which is almost negligible, is required to reduce the result of the copper dish test to any desired specification. Results of tests made with identical cracked gasolines with and without the addition of the stabilizing compound are shown hereunder:

COPPER DISH TESTS Sample 1 Amount of inhibitor Cum added (gms. per 100 cc.) (gins. per 100 cc.)'

Sample 2 Nil. 0. 183

group, is an exception. The presence of other groups in the benzene ring in addition to the above mentioned does not destroy the inhibiting action. I

All of the above mentioned substances except alpha-naphthol are more soluble in water than in oil, in which they are nearly insoluble, and they are not satisfactory for use in practice for the commercial stabilization of motor fuels on account ofthe fact that it is difiicult to prevent the latter irom coming into contact with water. Naphthol cannot be'used, since it causes motor fuel to deteriorate in color, although it is satisfactory as regards solubility.

I have found that if an alkyl or aryl group is substituted for a hydrogen atom in these compounds, their solubility in water is decreased and their solubility in oil is increased without an appreciable loss in their power to inhibit oxidation. The greater the number of alkyl or aryl groups which can be substituted in the benzene ring, the more soluble is the resulting compound inthe hydrocarbon to be stabilized and the less soluble in water. c

The new and novel features of the present invention are: the production of oil-soluble oxidation inhibitors from certain types of oil-insoluble phenolic or amino compounds, by substitution of one or more alkyl or aryl groups for hydrogen atoms; an improved method of introducing an alkyl group into a phenol; and the utilization of turpentine, a liquid sulphur dioxide extract of an oil, or the unsaturated hydrocarbons derived from the pyrolysis of oil or coal, as the base or stock from which the substituted phenolic or amino compound is produced; oils containing mixed unsaturated hydrocarbons are very much cheaper than the pure unsaturated compounds, but are equally satisfactory for the preparation of the substituted compound.

The introduction of alkyl groups is effected by a modification of the method of Koenigs (Ber.

alkyl substituted phenols by allowing a mixture of one part of the phenol with the equivalent 7 amount of an unsaturated hydrocarbon to stand instead of concentrated acid. This prevents loss of the phenolic compound by eliminating side reactions such as the formation of acetates.

3. The use of a much smaller quantity of sulphuric and'acetic acid, thus reducing the cost of manufacture.

4. Carrying out the reaction at an elevated temperature with agitation. This reduces the time required to a fewhours.

5. The use of a considerable excess of unsaturated compounds, in order to avoid loss of the more costly phenol.

6. Incomplete removal of acetic acid from the solution of alkyl substituted phenol. A trace of acid present in the solution acts as a preservative, preventing oxidation of the compound itself before it is added to the oil to be stabilized.

7. The use of a dilute solution of a mineral acid for extracting the acetic acid instead of water or ammonium carbonate. Oxidation of the compound during the washing is thus prevented.

It will be noted that by alkylation of the various oil-insoluble oxidation inhibitors, such as pyrogallol and aminophenol, in various ways, an almost infinite number of different compounds can be obtained which would be suitable for in- 23, 3144; 24, 1'79, 3889; 25, 2649) who prepared- Such oils, should 2. The use of dilute sulphuric acid (about 50%) hibiting the oxidation of oils. For the preparation of the various types of compounds, a number of different methods are available. For example, amyl pyrogallol may be prepared by the action of amyl alcohol on pyrogallol in the presence of anhydrous zinc chloride; and aminophenol can be alkylated by heating under pressure with alcohols; or the reaction between pyrogallol and unsaturated hydrocarbons will take place to some extent without a catalyst, or with aluminium chloride. I have, however, found that the cheapest and easiest compounds to manufacture are those prepared from pyrogallol by the method described above. Catechol also gives good results by this method, but is more expensive. Examples of the preferred method of preparation using cracked distillate and turpentine are given below:

Five parts by weight of powdered pyrogallol, ten parts of glacial acetic acid, one part of 50% sulphuric raid, and ten parts of cracked distillate are placed in an acid-resisting container fitted with a stirrer and a reflux condenser, and supplied with facilities for heating. The mixture is agitated violently, and heated to boiling. The agitation and heating are continued for two ,hours, 75 parts of cracked distillate being gradually added during this period. After two hours, when substantially all of the pyrogallol should have entered into combination with the unsaturated hydrocarbons present, the agitation is stopped and the product allowedto cool in an oxygen-free atmosphere. The reaction which occurs is probably as follows:

R.CH=CHz+CH3(OH)3=ROHgCHfLCQHflOH):

oleflne pyrogallol stabilizer The resulting mixture consists of a solution of the oxidation inhibitor and acetic acid in the oil which supplied the unsaturated hydrocarbons, and a layer of sludge on the bottom of the containing vessel. Twenty parts of 0.1% sulphuric acid are introduced, and the mixture is agitated for fifteen minutes for the purpose of removing excess acetic acid. The washing also causes any substituted compound contained in the sludge to return to the oil solution. The lower layer is drained off, and the extraction repeated twice. The solution of oxidation inhibitor thus prepared is then run into a storage vessel, preferably of copper or wood.

When turpentine is used, forty parts of pyrogallol are dissolved by heating and agitation in sixty parts of glacial acetic acid. One part of 50% sulphuric acid is added, and a hundred parts fresh turpentine introduced while the mixture is being agitated. Heat is evolved, and care must be taken that the temperature does not rise above 100 C. When all the turpentine has been added, the mixture is maintained at about 90 C. until the reaction is substantially complete. After cooling, it may be diluted by a suitable oil. It is then washed as in the previous example. The amount of the substituted compound formed is substantially twice the weight of pyrogallol used. I have found that acetic acid acts as a preservative of the compound, but most of it must be removed, as it would cause the motor fuel to which the above described inhibitor has been added to become corrosive. The acetic acid may be removed by extraction with any suitable solvent, such as water or a mineral acid, or by other suitable methods such as distillation; instead of by It has been found that the substituted compound when prepared as described above may be stored for a long period of time, at least as long as two years as shown by practical tests, without losing activity as a stabilizer.

I have found that a compound as thus prepared is acidic and that it can be removed or destroyed by shaking with alkalies, such as sodium carbonate or caustic soda. It is, therefore, necessary to prevent the motor fuel from coming into contact with alkaline substances after the addition of the inhibitor. The compound is also destroyed by organic peroxides, and to prevent this the motor fuel must be perfectly fresh and free from peroxides when the compound is added.

The gum content of Samples 3 and 4 shown hereunder has been determined by the U. S. Bureau of Mines steam oven method, in which a 20 cc. sample of motor fuel is evaporated in a steam oven from which oxygen is excluded. The gummy residue obtained in this manner is considered to represent the actual or inherent gum present in the fuel.

The gum content of Samples 1 and 2 hereinbefore described under copper dish tests was determined by evaporating 100 cc. of cracked gasoline on a steam bath. In this test the gasoline is exposed to atmospheric oxygen during the evaporation and although a sample of cracked gasoline gives a considerable residue by this method, the same sample might be found to be entirely free from inherent gum as determined by the steam oven method.

Results of storage tests made onidentical cracked gasolines, with and without addition of inhibitor, are given below. The samples consist of cracked gasoline stored in dark in glass bottles vented to atmosphere.

Sample No. 4

(weeks) Without With 0.0005% Without With 0.000595 inhibitor inhibitor inhibitor inhibitor 5 Nil. Nil. plus 25 plus 25 9 Trace. Nil. 25 25 13 Trace. 19 .001 24 .006 30 36 42 48 54 77 83 This application is a division of my co-pending application, Serial No. 503,095, filed December 17, 1930.

From the above description it will be evident that while I have described and claimed the preferred embodiment of the invention, it is to be understood that I reserve the right to make all changes properly falling within the spirit of the invention and without the ambit of the prior art.

I claim:

1. A cracked gasoline, normally tending to deteriorate and form gum on storage, containing a substituted polyhydric phenol containing components of turpentine as substituted groups in sufiicient quantity to substantially stabilize the distillate against such deterioration and gum formation.

2. The product substantially as described in claim 1 in which the polyhydric phenol is pyrogallol.

3. The product substantially as described in claim 1 in which the polyhydric phenol is cate- 4. The method of stabilizing against deterioration and gum formation a cracked hydrocarbon distillate, which comprises adding to the distillate a substituted polyhydric phenol containing components of turpentine as substituted groups, in sufficient quantity to substantially retard such deterioration and gum formation.

CHARLES P. WILSON, JR. 

